如何取消订阅 C# 中特定类的事件的所有处理程序? [英] How do I unsubscribe all handlers from an event for a particular class in C#?

问题描述

基本前提:

我有一个房间，当一个头像进入"房间内的所有头像时，它会发布一个事件.当头像离开房间时，我希望它删除该房间的所有订阅.

I have a Room which publishes an event when an Avatar "enters" to all Avatars within the Room. When an Avatar leaves the Room I want it to remove all subscriptions for that room.

在将 Avatar 添加到新 Room 并订阅新 Room 的事件之前，如何最好地从 Room 中的所有事件取消订阅 Avatar?

How can I best unsubscribe the Avatar from all events in the room before I add the Avatar to a new Room and subscribe to the new Room's events?

代码如下:

class Room
{
   public event EventHandler<EnterRoomEventArgs> AvatarEntersRoom;
   public event EvnetHandler<LeaveRoomEventArgs> AvatarLeavesRoom;
   public event EventHandler<AnotherOfManyEventArgs> AnotherOfManayAvatarEvents;


   public void AddPlayer(Avatar theAvatar)
   {
      AvatarEntersRoom(this, new EnterRoomEventArgs()); 

      AvatarEntersRoom += new EventHandler<EnterRoomEventArgs>(theAvatar.HandleAvatarEntersRoom);

      AvatarLeavesRoom += new EventHandler<EnterRoomEventArgs>(theAvatar.HandleAvatarEntersRoom);

      AnotherOfManayAvatarEvents += new EventHandler<EnterRoomEventArgs>(theAvatar.HandleAvatarEntersRoom);          

   }

}

class Avatar
{
   public void HandleAvatarEntersRoom(object sender, EnterRoomEventArgs e)
   {
       Log.Write("avatar has entered the room");
   }

   public void HandleAvatarLeaveRoom(object sender, LeaveRoomEventArgs e)
   {
       Log.Write("avatar has left room");
   }

   public void HandleAnotherOfManayAvatarEvents(object sender, AnotherOfManyEventArgs e)
   {
       Log.Write("another avatar event has occurred");
   }
}

推荐答案

每个委托都有一个名为 GetInvocationList() 的方法，该方法返回所有已注册的实际委托.所以，假设委托类型(或事件)被命名为 MyDelegate，并且处理程序实例变量被命名为 myDlgHandler，你可以这样写:

Each delegate has a method named GetInvocationList() that returns all the actual delegates that have been registered. So, assuming the delegate Type (or event) is named say MyDelegate, and the handler instance variable is named myDlgHandler, you can write:

Delegate[] clientList = myDlgHandler.GetInvocationList();
foreach (var d in clientList)
       myDlgHandler -= (d as MyDelegate);

覆盖它可能为空的情况，

to cover the case where it might be null,

 if(myDlgHandler != null)
  foreach (var d in myDlgHandler.GetInvocationList())
       myDlgHandler -= (d as MyDelegate);

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